altruism, and conformity, has a synergistic effect with the role of neurobiology in influencing decision making.

Dr. Wilkinson explored the mechanism of group dynamics and its role in the contagion of violence. She echoed the comments of several speakers in noting the importance of schemas, scripts, attribution, collective responsibility, conformity, and imitation, and explored these within the context of group violence. In particular, she noted the strong influence of peers and an individual’s reputation.

Group affiliation, such as in gangs, is correlated with increased risk of violence, as victim, perpetrator, or witness. Often, these groups exist within a social ecology in which allegiance is seen as protective against outside danger (Wilkinson and Carr, 2008). As previously noted, youth create their identities through observational learning and socialization, and much of the violence that occurs within groups is public. Dr. Wilkinson especially noted that expectations of behavior are created collectively, versus individually. This is more than peer pressure, she argues, but also a diffusion of responsibility throughout the group. Thus, social integration brings with it the scripts and schemas that underlie behavior.

In unpacking the violent event, Dr. Wilkinson noted that in her research she was very interested in knowing what was occurring in the participants’ minds, and also in the co-occurrences of the event. In one study of hers, she noted two major additional factors: (1) the presence of a third party, and (2) the gossip that occurs before and after the event. Both speak to peers and reputation, and the status of the antagonists and protagonists within the group. She also pointed out the implication of retaliation, which she noted occurred about one third of the time. From this research, she posits five types of peer group influence related to violence, with implications for why violence spreads:

1. Planning involvement in advance

2. Coming to the aid of an associate who is losing

3. Being an observer who is threatened during the interaction

4. Seeking justice or righting a perceived wrong

5. Addressing gossip to protect reputation

Social Influence and Intersectionality

At the macro level, factors within society influence not only how and when violence occurs, but also how it might be transmitted. Speaker Anita Raj of the University of California, San Diego, discussed the interaction of multiple social factors in the context of intimate partner violence. She noted that her original research in HIV prevention indicated that expectations of behavior based solely on social-cognitive models would not always

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